Donald Trump vowed Thursday to wage a hard-charging and lengthy presidential campaign, including filing his financial disclosures with the Federal Election Commission as early as next week, as unease continued to swirl throughout the Republican Party about his incendiary rhetoric on immigration.

In a wide-ranging, 30-minute interview with The Washington Post, the billionaire real estate mogul and reality-television star also said he has serious concerns about other GOP candidates and refused to commit to supporting the eventual nominee in the general election.

“So many people want me to run as an independent, so many people,” Trump said. “I have been asked by — you have no idea, everybody wants me to do it.”

Pressed about whether he would back the Republican ticket if he fails to win the nomination himself, Trump left the door open for a third-party bid of his own. “I would have to see who the nominee is,” he said.

For now, Trump said, he thinks that the “best chance of defeating the Democrats” is for him to “win as a Republican because I don’t want to be splitting up votes.”

The specter of an independent run by Trump has unnerved GOP power brokers, many of whom worry that such a campaign could draw substantial support from the party’s base, similar to how Ross Perot’s maverick 1992 presidential campaign won an enthusiastic following among frustrated conservatives.

Trump’s comments came in a call to The Post to dispute some details reported Wednesday night about a private phone call with Reince Priebus, chairman of the Republican National Committee.

Trump said that the Wednesday call with Priebus lasted between 10 and 15 minutes and was “congratulatory” with regard to Trump’s ascent in the polls. He said that, near the end of their discussion, Priebus asked him to speak in a more measured way about immigration.

“He started off saying, ‘Wow, you really hit a nerve,’ ” Trump said. “He said, ‘I don’t think I’ve ever seen anything like this since I’ve been in politics.’ ”

Trump added, “Then, in closing, he said, ‘You know, if it would be possible, maybe you could tone it down just a little bit, but you are who are you, and I know you have to do what you have to do.’ ”

Trump said the call from Priebus “was meant, in my opinion, to be a congratulatory call. . . . It wasn’t a lecturing-type call. He’s going to lecture me? Give me a break.”

Priebus’s outreach to Trump came after days of talks with GOP leaders about how best to manage Trump’s seemingly nonstop appearances on cable news programs and his unrelenting commentary on illegal immigration. Donors familiar with the exchange told The Post about the call on Wednesday and said it lasted for about 45 minutes. A spokesman for the RNC later confirmed the call on the record.

Trump called Priebus “a very nice man” but said he has “a lot of different constituents” in Republican ranks and suggested that the party chairman may have wanted to make it seem to others in the party that he had been “tougher” on the call than he was, in Trump’s view.

Trump shrugged off the alarm in GOP quarters about his candidacy. “They don’t know me yet,” Trump said of Republican elders. “When they know me, they will love me. That’s what happens, and I think I’m going to win. I’m getting the biggest crowds by far. I’m going to Arizona [on Saturday]. I hear the place is going wild.”

One Arizona Republican who is not cheering is Sen. Jeff Flake, who on Thursday called on the local Republican Party to withdraw its sponsorship of the event, which will feature Trump and Maricopa County Sheriff Joe Arpaio.

In an interview Thursday, Flake said both Trump and Arpaio’s inflammatory words about immigrants and about President Obama’s place of birth are not indicative of the Republican Party’s values. The event at the Arizona Biltmore in Phoenix is hosted by the Republican Party of Maricopa County.

“As an elected official and as a Republican, I’m not excited about this, to say the least,” Flake said. “I don’t think that [Trump’s] views are reflective of the party, particularly in Arizona, a border state.”

Other Republicans disagreed. “I believe that Mr. Trump is kind of telling it like it really, truly is,” former Arizona governor Jan Brewer told CNN on Wednesday. She said many residents are anxious about “the drug cartels, the smugglers, the drug houses” that “come across our border.”

In the Thursday interview, Trump repeatedly noted his rapid rise in the polls, both nationally and in early caucus and primary states. “My life has not been losing, you understand that,” Trump said. “They used to say ‘clown.’ I’m not a person that loses. I don’t lose.”

And Trump declared several times that he would “win the Latin vote — win the Latino vote.”

But he posited that he would consider dropping out of the race if he senses that he cannot win.

“I have a huge staff — I have a big staff in Iowa, New Hampshire, all over,” Trump said. “I absolutely stay in. If for some reason I think it’s not going to happen, I’m not a masochist. You understand that, right? . . . I’m a smart person. I went to the Wharton school of finance. I built a great company.”

Trump renewed his attacks on Democratic front-runner Hillary Rodham Clinton, saying that “she did a bad job as secretary of state.” He said she and her husband, former president Bill Clinton, once were friends of his, but “I haven’t spoken to Hillary in years.”

Asked to assess Clinton’s presidency, Trump said, “He would’ve been a very good president had he not met Monica [Lewinsky] and the others.”

Turning to the first GOP primary debate, scheduled for Aug. 6 in Cleveland, Trump said he is planning to be onstage. Fox News is requiring that candidates file their financial disclosures with the FEC to qualify.

Asked whether he plans to meet that requirement, Trump said, “Of course I am.” He said he is entitled to two 45-day extensions with the FEC, but said he will not use them and plans to submit his paperwork in the coming days, perhaps next week.

Trump has not begun to prepare for the debates, however. “I’m not a debater,” he said. “I don’t debate. I build buildings, and I grow jobs. These [other candidates] debate every [expletive] night of their life. That’s all they do. They talk.”

Trump suggested that Mitt Romney spent too much time readying for forums as the 2012 Republican nominee.

“He became a frozen jellyfish,” Trump said. “He spent so much time in prep he couldn’t speak.”